1. Field
The embodiments relate to an internal power supply circuit, and in particular relates to an internal power supply circuit, the startup time of which is shortened, and which avoids wasteful power consumption.
2. Description of the Related Art
Semiconductor integrated circuits, and particularly DRAM devices, have an internal power supply circuit to generate an internal step-down power supply from an external power supply, in order to achieve both fast operation and low power consumption. The internal circuitry operates by means of the internal step-down power supply. In the case of DRAM, the internal power supply circuit generates a first internal step-down power supply voltage Vii lower than the external power supply voltage Vdd, and generates second internal step-down power supply voltages Vpr, Vcp lower than the first internal step-down power supply voltage Vii. The internal power supply circuit also generates an internal step-up power supply voltage Vpp higher than the external power supply voltage Vdd.
The first internal step-down power supply voltage Vii is supplied to the DRAM peripheral circuitry, and is also supplied to the memory core having a memory cell array. The second internal step-down power supply voltages Vpr, Vcp and the internal step-up power supply voltage Vpp are supplied to the memory core.
The first internal step-down power supply voltage Vii is generated from the external power supply voltage Vdd, while the second internal step-down power supply voltages Vpr, Vcp are generated from the first internal step-down power supply voltage Vii.
For the above reasons, at the time of power supply startup, the internal power supply circuit monitors the rise of the external power supply voltage Vdd, and after detecting the rise of this voltage starts the first internal step-down power supply generation circuit. Further, the internal power supply circuit monitors the rise of the first internal step-down power supply voltage Vii, and after detecting the rise of this voltage starts the second internal step-down power supply generation circuit. And, when the rise of the second internal step-down power supply voltages Vpr, Vcp is detected, the internal power supply circuit outputs a start signal indicating that the series of internal power supply startup operations has ended. In response to this start signal, the internal circuitry begins operation.
Internal step-down power supply generation circuits are disclosed in Japanese Patent Laid-open No. 2001-28188 and Japanese Patent Laid-open No. 09-62380. In Japanese Patent Laid-open No. 2001-28188, a circuit is disclosed which generates two internal step-down power supply voltages; in Japanese Patent Laid-open No. 09-62380, an internal step-down power supply circuit is disclosed.